but military action would not be easy. it could take upwards of 75,000 troops to secure those chemical weapons, which no one is eager to provide. but president obama, diane, has warned that using those weapons is a red line. >> on the story for us tonight, martha raddatz, thank you, martha. >>> and now, we want to tell you about another turbulent hot spot, so vital to the united states. there is a battle in the streets outside the presidential palace in egypt, again. and abc's nick schifrin is there. >> reporter: tonight, 10,000 egyptians taking the fight over their future to the presidential palace. they want president mohamed morsi, the man they elected, now to be removed for seizing too much power. last night, the same street was a war zone. six killed, 700 injured. the biggest crisis here since egypt, one of america's most important arab allies, overthrew its dictator, hosni mubarak. these very same people filled these same streets two years ago. today, they are chanting the exact same songs, only replacing mubarak's n